The present disclosure relates to a coordinate measuring machine, and more particularly to a portable articulated arm coordinate measuring machine having multiple independent buses.
Portable articulated arm coordinate measuring machines (AACMMs) have found widespread use in the manufacturing or production of parts where there is a need to rapidly and accurately verify the dimensions of the part during various stages of the manufacturing or production (e.g., machining) of the part. Portable AACMMs represent a vast improvement over known stationary or fixed, cost-intensive and relatively difficult to use measurement installations, particularly in the amount of time it takes to perform dimensional measurements of relatively complex parts. Typically, a user of a portable AACMM simply guides a probe along the surface of the part or object to be measured. The measurement data are then recorded and provided to the user. In some cases, the data are provided to the user in visual form, for example, three-dimensional (3-D) form on a computer screen. In other cases, the data are provided to the user in numeric form, for example when measuring the diameter of a hole, the text “Diameter=1.0034” is displayed on a computer screen.
An example of a prior art portable articulated arm CMM is disclosed in commonly assigned U.S. Pat. No. 5,402,582 ('582), which is incorporated herein by reference in its entirety. The '582 patent discloses a 3-D measuring system comprised of a manually-operated articulated arm CMM having a support base on one end and a measurement probe at the other end. Commonly assigned U.S. Pat. No. 5,611,147 ('147), which is incorporated herein by reference in its entirety, discloses a similar articulated arm CMM. In the '147 patent, the articulated arm CMM includes a number of features including an additional rotational axis at the probe end, thereby providing for an arm with either a two-two-two or a two-two-three axis configuration (the latter case being a seven axis arm).
In contemporary AACMMs, measurement data, including encoder data, is collected and transmitted along an arm bus located in the articulated arm CMM. A drawback to the use of a single bus is that characteristics of the bus, such as bus speed and bus width, are dictated by requirements of the encoders and the encoder data. Another drawback to the use of a single bus is that the amount of non-encoder data that can be sent on the arm bus is limited by the remaining capacity on the arm bus after taking into account the capacity used by the encoder data. While existing AACMMs are suitable for their intended purposes, what is needed is a portable AACMM that has certain features of embodiments of the present invention to provide an enhanced arm bus.